1. Field of the Invention
The present invention relates to a lubricant for thermoplastic resins, and a thermoplastic resin composition comprising the lubricant. This thermoplastic resin composition has an excellent mold release characteristics at the molding step and can give a good gloss to a molded article.
2. Description of the Related Art
Since thermoplastic resins have good physical and chemical characteristics, they are widely used as films, sheets, wall materials, interior and exterior materials of automobiles, household electric appliances and the like. However, thermoplastic resins such as a vinyl chloride polymer resin, an ABS resin, a styrene polymer resin, and an acrylic resin have problems such that various processability characteristics are poor. As means for eliminating this defect, there has been adopted a method in which a thermal stabilizer, a processing aid such as a copolymer composed mainly of methyl methacrylate, a plasticizer, a mold release agent, a lubricant and the like are incorporated. However, this method cannot become a general solution of the problem.
Accordingly, various research and development has been carried out to solve the above problem, and vinyl chloride polymer resin compositions as disclosed in Japanese Examined Patent Publications Nos. 52-781, 52-3668 and 50-23067 have been proposed.
In the above-mentioned compositions, the inherent transparency of a vinyl chloride polymer resin is retained, the moldability such as drawdown, the flowability at the molding step, and the elongation at a high temperature are improved, and lubricating properties such as releasing from the roll surface at the calendering step can be maintained for a long time. However, in order to improve the productivity and quality, and from the energy-saving viewpoint, it is desirable to develop a processing aid capable of giving a durable lubricating property to a vinyl chloride polymer resin at the processing step, and this desire is not sufficiently satisfied in the above-mentioned compositions. Moreover, an increase of substances adhering to molds (plateout) is observed under some molding and processing conditions. Accordingly, the above-mentioned compositions fail to sufficiently satisfy commercial requirements.